The present invention relates to an evaluation method and apparatus which evaluate the optical performance and surface shape of a spectacle lens or those of a mold used for spectacle lens molding, and a spectacle lens manufacturing method and system which use the evaluation method and apparatus.
A spectacle lens is manufactured and processed in accordance with optimized specifications from a designer. It is necessary to make an evaluation after manufacturing to check whether the finished spectacle lens complies with the specifications. As a method of measuring the optical performance of a spectacle lens, a measurement method using a lens meter is available. In measurement with the lens meter, the dioptric power or the like of a lens is measured by vertically projecting a parallel light beam on a lens surface. A lens meter for measuring an addition is also known. Measurements with these lens meters are generally spot measurements.
As greater importance has recently been placed on the optimization of peripheral vision (aberration), demands have arisen for the evaluation of the optical performance of a lens throughout a wide range. When controlling the quality of products, it is important to check how much error a lens manufactured on the basis of design data has with respect to the design data. Lens shapes greatly vary in terms of surface shape and material even with the same prescription. In addition, there has been a trend toward customization, resulting in diversification of lens shapes. In the case of customization, a lens shape is determined by a prescription presented at the time of an order received and other parameters (e.g., framing shape, lens material, and lens thickness). The lens is processed on basis of the design values. The resultant lens is then delivered to the customer. It is required to further shorten the time interval from the determination of a lens shape to the delivery of the lens by reducing time and labor required for tests.
In order to measure the optical performance of a lens in a wide range by using the above lens meter and compare it with design values, since spot measurement is performed with the lens meter as described above, measurement must be done at many points. This measurement requires much time and labor. In addition, the value measured by the lens meter is a dioptric power (refractive power), whereas design values are three-dimensional shape data. Therefore, the design values cannot be easily compared with the dioptric power actually measured by the lens meter. In performing such comparison, a dioptric power at each position in three-dimensional shape data as design values is calculated in advance, and each calculated dioptric power is compared with the dioptric power actually measured by the lens meter. As described above, however, since lenses have greatly diversified due to the trend of customization, it is practically difficult to calculate the dioptric powers of all lenses in wide ranges in advance.
Recently, there has been proposed an apparatus for measuring and evaluating the optical characteristics of a spectacle lens in a wide range. For example, an evaluation apparatus for measuring the three-dimensional shape of a lens is known as disclosed in Japanese Patent Laid-Open No. 2000-186978. However, this evaluation apparatus uses a contact type three-dimensional measuring device, a long time is required for measurement.
In addition, an apparatus for measuring the three-dimensional shape and dioptric power distribution of a lens in a noncontact manner is also known as disclosed in PCT(WO) 10-507825 and Japanese Patent Laid-Open No. 8-304228. Such an apparatus can measure the optical characteristics of a lens in a wide range within a short period of time. In order to compare measured values with design values, the optical characteristic based on design values must be calculated in advance. It is therefore difficult to calculate the optical characteristics of all kinds of lenses in great variety in advance.
A mold used for molding a spectacle plastic lens is made of glass, and its molding surface is transferred to a plastic lens. The molding surface of the mold must therefore have as high surface precision as that of the glass lens. Consequently, it is necessary to measure and evaluate the surface shape of the mold. Evaluating a mold poses the same problems as in the case of a lens.